Page:EB1911 - Volume 14.djvu/673

Rh organs and the vent, although close together, are yet distinct. In the musk-shrews (Crocidura), on the other hand, which are common to Europe, Asia and Africa, the reproductive organs and the alimentary canal discharge into a common cloaca, the long tail is sparsely covered with long and short hairs, there are anal glands secreting a strong musky fluid, and the number of upper teeth is 16 or 18. Diplomesodon pulchellus of the Kirghiz steppes, has, on the other hand, only 14 upper teeth, and is further characterized by the moderately long tail and the hairy soles of the hind-feet. Another genus is represented by the Tibetan Anurosorex squamipes, which has the same dental formula, but a mole-like form, rudimentary tail and scaly hind-soles. Lastly, we have two Asiatic mountain aquatic species, Chimarrogale himalayaca of the Himalayas and Nectogale elegans of Tibet, which have fringed tails like the European water-shrew, and 16 upper teeth, the former characterized by the small but perfect external ears, and the latter (fig. 6) by the absence of the ears and presence of adhesive disks on the feet.

It will be seen that the red- and the white-toothed series have parallel representative forms, which may indicate that the division of the family into the two groups is one based rather on convenience than on essential differences. See.

From the shrews, the hedgehogs and gymnuras, or rat-shrews, collectively forming the family Erinaceidae, differ structurally by the broader ring made by the tympanic, the complete zygomatic arch, the five-cusped broad upper molars, and the presence of a short pubic symphysis. At the present day they are an exclusively Old World group.

The typical group, or Erinaceinae, is represented only by the hedgehogs, with the one genus Erinaceus, easily recognized by their spiny coats, and further characterized by the rudimentary tail, the presence of vacuities in the palate, and the broad pelvis. Hedgehogs (Erinaceus) have the dental formula

i., c. , p. , m. , and are represented by over a score of species, distributed throughout Europe, Africa and the greater part of Asia, but unknown in Madagascar, Ceylon, Burma, Siam, the Malay countries, and, of course, Australia. All the species resemble one another in the armour of spines covering the upper surface and sides of the body; and all possess the power of rolling themselves up into the form of a ball protected on all sides by these spines, the skin of the back being brought downwards and inwards over the head and tail so as to include the limbs by the action of special muscles.

Curiously enough the European hedgehog (E. europaeus) is the most aberrant species, differing from all the rest in the peculiarly-shaped and single-rooted third upper incisor and first premolar (fig. 7, A), and in its very coarse harsh fur. The dentition of the long-eared Indian E. grayi (fig. 7, B) may, on the other hand, be considered characteristic of all the other species, the only important differences being found in the variable size and position of the second upper premolar, which is very small, external and deciduous in the Indian E. micropus and E. pictus. The former species, limited to South India, is further distinguished by the absence of the jugal bone. Of African species, E. diadematus, with long frontal spines, is probably the commonest, and E. albiventris has been made the type of a separate genus on account of the total absence of the first front-toe. See.

The members of the second subfamily, Gymnurinae, are more or less rat-like animals, confined to the Malay countries, and easily distinguished from the hedgehogs by the absence of spines among the fur and the well-developed tail. They also lack vacuities in the palate, and have a long and narrow pelvis.

The typical representative of the family is the greater rat-shrew, or greater gymnura (Gymnura rafflesi) a creature which may be compared to a giant shrew, and whose colour is partly black and partly white, although a uniformly pale-coloured race. (G. r. alba) inhabits Borneo. In common with the next genus, it has the full series of 44 teeth; and its range extends from Tenasserim and the Malay Peninsula to Sumatra and Borneo, the island individuals being stated to be considerably larger than those from the mainland. In this species the length of the tail is about three-fourths that of the head and body; but in the lesser rat-shrew (Hylomys suillus), ranging from Burma and the Malay Peninsula to Java and Sumatra, the former dimension is only about one-sixth of the latter. In the Philippines the group is represented by Podogymnura truei, distinguished from the other genera by the great elongation of the hind-foot, the tail being likewise long. There are only three pairs of premolars in each jaw.

In the remaining families of the Insectivora the tibia and fibula may be either separated or united at the lower end; there is no descent of the testes, except in Solenodon; a short symphysis is formed by the junction of the pubic epiphyses; and the upper molars are generally small, and

triangular, with three cusps arranged in a V. The first family, Potamogalidae, is represented by the otter-like Potamogale velox of the rivers of West Africa (fig. 8), distinguished from all other members of the order by the absence of clavicles. The tibia and fibula are united interiorly, the skull has a ring-like tympanic, no zygomatic arch, and the upper molars are of the tuberculo-sectorial type, with broader crowns than in the following families. The dental formula is i., c. , p. , m. , total 40. This animal inhabits the banks of streams in west equatorial Africa, and its whole structure indicates an aquatic life. It is nearly 2 ft. in length, the tail measuring about half. The long cylindrical body is continued uninterruptedly into the thick laterally compressed tail, the legs are very short, and the toes are not webbed, progression through the water depending wholly on the action of the powerful tail, while the limbs are folded inwards and backwards. The muzzle is broad and flat, and the nostrils are protected by valves. The fur is dark brown